In the making of metal cans, such as aluminum cans of the type typically used for beverages, it is common practice to form the bodies of the cans from pre-drawn cup-shaped blanks in a body making apparatus. The cup-shaped blanks are transformed into can bodies by striking the blanks with a punch ram and forcing them through a series of progressive dies that, in essence, stretch and elongate the sidewalls of the blanks. The punch ram typically is carried on a reciprocating ram carriage that is rollably movable on a horizonal way system. The punch ram is moved on the horizonal way system by a rotating crankshaft that is driven by a motor and flywheel.
A body making apparatus also typically includes a feeder mechanism for segregating a single cup blank from queued plurality of cup blanks and placing the single cup blank into a locator structure that aligns and properly positions the blank to be contacted by the punch ram. One common type of feeder mechanism in contemporary commercial use is a rotary cup blank feed in which the pre-drawn cup blanks are loaded from the top and indexed to a position adjacent to a rotating cam. When the cup blank is properly aligned and positioned, a redraw sleeve, carried by a redraw carriage, is moved into the internal portion of the cup blank into concentric relationship with the sidewall of the cup blank. The punch ram thereafter is moved through the redraw sleeve to contact the bottom of the cup blank and to force the blank through the series of progressive dies. It is critically important to properly and accurately feed and place the cup blank in the locator structure before it is contacted by the punch ram. Misfeeding the blank will cause the redraw sleeve to "clip out" or otherwise tear the sidewalls of the cup blank, and the punch ram will force the torn metal into the dies. Such action not only destroys the cup blank, it also can cause serious damage to the dies and the punch ram.
It obviously is important to synchronize the movement of the feeder mechanism with the movement of the punch ram so that the cup blank is placed in the locator structure in timed relationship with the stroke of the punch ram. In order to insure the necessary phased relationship between the rotation of the crankshaft, which moves the ram carriage, and the feeder mechanism, prior art body making machines have mechanically interconnected the drive train of the feeding mechanism to the drive train of the ram carriage. However, the feeder mechanism must, of necessity, be located proximal to the locator structure, which usually is at the opposite end of the body making machine from the crankshaft. The feeder mechanism also is at a different elevation than the crankshaft. Thus, when the feeder mechanism and the ram carriage have been driven by a common drive and mechanically interconnected in the past, it has been necessary to transmit the driving power for the feeder mechanism through a series of gears or couplings, each of which permits some unintended relative movement or "looseness" between relatively moving adjacent components. More particularly, prior art feeder mechanisms are driven by and timed through a series of chains, sprockets, shafts and gearboxes with the crankshaft which drives the punch ram. While the arrangements for mechanically interconnecting the punch ram crankshafts and the feeder mechanism cams in the prior art generally have proved highly successful, several problems remain. It is difficult to keep the feeder mechanism cam in time with the crankshaft with such arrangements due to the number of inputs and outputs that the power goes through before it gets to the feeder mechanism cam. Moreover, for purposes of controlling the timing of the movement between the punch ram crankshaft and the feeder mechanism, the amount of relative movement between each of the components of the sprockets, chains and gears in the drive train to the feeder mechanism is cumulative. As a consequence of this relative movement between the drive train components, it sometimes occurs that the critical phase relationship between the movement of the punch ram crankshaft and the feeder mechanism is lost. Such loss of this critical phase relationship results in a misfeed of a cup blank, and the damage of the blank, punch ram and dies discussed above. The problems of "looseness" between the drive train components is one that is compounded when the components experience wear. Furthermore, all of the chains, sprockets, shafts and gearboxes used for these drive trains require high levels of maintenance.
Moreover, the damage from the misfeed of a cup blank normally is not limited to that resulting from the destruction of a single blank cup. The mass of the ram carriage typically is so great in prior art body making machines that it is not feasible to adequately brake the movement of the punch ram once a misfeed occurs and is detected. Thus, in prior art machines, the punch ram, will generally make two to three strokes after the misfeed is detected. While the feeder mechanisms of the prior art generally include escapement systems that limit the number of cup blanks being feed to the locator structure, there is typically at least one additional cup blank, in addition to the misfed cup blank that is feed to the locator structure after the misfeed. Since fragments of the misfed cup blank will remain in the locator structure and dies, the subsequently fed cup blank also is destroyed as it is contacted by the punch ram, and the metal from the subsequent cup blank further damages the punch ram and the dies.